Re: [Linaro-mm-sig] Changing vma->vm_file in dma_buf_mmap()
From: Jason Gunthorpe
Date: Thu Sep 17 2020 - 12:40:20 EST
On Thu, Sep 17, 2020 at 06:06:14PM +0200, Christian König wrote:
> > > If it is already taking a page fault I'm not sure the extra function
> > > call indirection is going to be a big deal. Having a uniform VMA
> > > sounds saner than every driver custom rolling something.
> > >
> > > When I unwound a similar mess in RDMA all the custom VMA stuff in the
> > > drivers turned out to be generally buggy, at least.
> > >
> > > Is vma->vm_file->private_data universally a dma_buf pointer at least?
> > Nope. I think if you want this without some large scale rewrite of a
> > lot of code we'd need a vmops->get_dmabuf or similar. Not pretty, but
> > would get the job done.
> Yeah, agree that sounds like the simplest approach.
I don't think that will fly, it is clearly only papering over a mess
inside DRM/dma buf :\